Note: modern applications may prefer to use the interfaces described
in utimensat(2).
The utime() system call changes the access and modification times of
the inode specified by filename to the actime and modtime fields of
times respectively.
If times is NULL, then the access and modification times of the file
are set to the current time.
Changing timestamps is permitted when: either the process has
appropriate privileges, or the effective user ID equals the user ID
of the file, or times is NULL and the process has write permission
for the file.
The utimbuf structure is:
struct utimbuf {
time_t actime; /* access time */
time_t modtime; /* modification time */
};
The utime() system call allows specification of timestamps with a
resolution of 1 second.
The utimes() system call is similar, but the times argument refers to
an array rather than a structure. The elements of this array are
timeval structures, which allow a precision of 1 microsecond for
specifying timestamps. The timeval structure is:
struct timeval {
long tv_sec; /* seconds */
long tv_usec; /* microseconds */
};
times[0] specifies the new access time, and times[1] specifies the
new modification time. If times is NULL, then analogously to
utime(), the access and modification times of the file are set to the
current time.

EACCES Search permission is denied for one of the directories in the
path prefix of path (see also path_resolution(7)).
EACCES times is NULL, the caller's effective user ID does not match
the owner of the file, the caller does not have write access
to the file, and the caller is not privileged (Linux: does not
have either the CAP_DAC_OVERRIDE or the CAP_FOWNER
capability).
ENOENT filename does not exist.
EPERM times is not NULL, the caller's effective UID does not match
the owner of the file, and the caller is not privileged
(Linux: does not have the CAP_FOWNER capability).
EROFS path resides on a read-only filesystem.

This page is part of release 3.81 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
http://www.kernel.org/doc/man-pages/.
Linux 2014-08-19 UTIME(2)